泛肽交联酶（E2）通过苯丙氨酸解氨酶基因启动子参与水稻对紫外光的防护

迄今为止，诱导苯丙类化合物和黄酮类化合物合成并造成类黄酮的积累被认为是植物抵御紫外光的惟一主要的途径。苯丙氨酸解氨酶(PAL)是苯丙类化合物合成的关键酶。通过体内足印试验表明，在pal-1基因启动子中有一段序列CTCCAACAACCCCCTTC可以作为顺式元件参与紫外信号的传递。为了克隆与其相对应的反式因子，我们使用了酵母单杂交体系进行筛选。在鱼饵质粒中，我们将3个拷贝的顺式元件序列串联并与酵母异细胞血红素C(CYC)基本启动子连接。将鱼饵质粒和水稻cDNA表达质粒库共同转化到同一酵母中，通过筛选鉴定，克隆到一些编码泛肽交联酶(E2)基因。氨基酸同源性分析表明，该酶E2(RE2)与其他物种的泛肽交联酶具有很高的同源性。水稻泛肽交联酶受紫外光诱导加速合成。当RE2与水稻核蛋白进行交联反应后能与pal-1基因中顺式元件CTCCAACAACCCCTTC专一结合。从这些结果可以推测水稻泛肽交联酶RE2可能通过苯丙类化合物的合成代谢参与对紫外光的防护。

Ubiquitin-Conjugating Enzyme (E2) Confers Rice UV Protection Through Phenylalanine Ammonia-Lyase Gene Promoter Unit

The induction of general phenylpropanoid and flavonoid glycoside pathways and the consequential accumulation of UV protective flavonoids so far have been regarded as the only major metabolic response to UV light. Phenylalanine ammonia-lyase (PAL) is a key enzyme of phenylpropanoid metabolism. Inducible in vivo footprints in the pal -1 promoter defined the motif CTCCAACAACCCCTTC as a cis-element that transmits the UV signal. In order to clone its corresponding trans-acting element, three copies of the motif were synthesized and used as a bait of yeast one-hybrid system. A number of genes coding ubiquitin-conjugating enzyme-like proteins (E2) were isolated from a rice cDNA library by the system. The rice (Oryza sativa L) E2 (RE2) was high homology to other E2 of different species and can be induced by UV light. RE2 can react with nuclear extraction protein and binds the pal-1 promoter cis-element. These results suggest that RE2 takes part in plant response to UV stress through regulating the phenylpropanoid metabolism.